a) Field of the Invention
The invention is directed to a leveling system for household appliances, such as washing machines, comprising appliance feet which are arranged at the underside of the household appliance and which are adjustable in height at least partly by means of an actuation member and therefore make it possible to adjust the height of the household appliance and/or to adapt to unevenness in floors, wherein the actuation member is a traction element and the appliance feet which are adjustable in height by means of the traction element have, in each instance, a cylindrical housing fastened to the underside of the household appliance, in which cylindrical housing there is arranged a piston which carries the appliance foot plate, wherein the traction element joins the pistons of the appliance feet that are adjustable in height by means of the traction element.
b) Description of the Related Art
A leveling system for installable or stackable household appliances in which the height adjustment at least of the rear appliance feet can be carried out from the front side of the appliance by means of an actuation device is already known from DE 35 19 479 A1. For this purpose, there is an actuation member that is accessible to the user and that communicates with the rear appliance feet via a closed liquid system. With this known device, household appliances whose appliance feet are no longer accessible at their rear end after the household appliances have been integrated or stacked underneath in a kitchen installation can also be adapted in a corresponding manner with respect to installation height.
It is disadvantageous that it is relatively difficult to keep the arrangement liquid-tight.
Arrangements working with mechanical gear units are also already known, e.g., from DE 196 06 460 A1. However, appliance feet that are provided with mechanical gear units in this way are relatively elaborate and expensive and are sometimes also difficult to operate.
According to EP 0 544 175 A1, the problem of compensating for differences in height due to uneven floors with inaccessible appliance feet is solved by arranging a spring element between an upper part of the foot and a lower part on the floor side. However, it is admitted in the reference that a correct choice of spring element based upon the weight of the appliance is necessary. When dynamic loading occurs in addition to the static load, the reference proposes connecting an elastically deformable element in parallel to the spring. However, a foot of this type which is individually spring-mounted and provided with mechanical damping is dependent upon the weight of the appliance and therefore cannot be used for a stacked configuration, that is, it cannot be applied in vertically oriented washer/dryer combinations.
This is also true of a self-adjusting, displaceable foot arrangement known to the present applicant which comprises a spring/damping element and a conventional appliance foot. The biased or pre-tensioned spring which is accommodated in a cylindrical housing acts on the damping element and on the appliance foot and compensates for unevenness in floors up to about +/−10 mm. Stable operation of the automatic machine is achieved by means of a load-dependent shock absorbing function. The spring/damping element is designed for installation inside of the appliance housing at the rear right-hand or rear left-hand side depending on the loading of the foot and based on the drum dynamics in combination with the suspension of the washing machine drum and its distribution of mass. Fastening (by screwing) of the foot of this automatic machine is carried out from the underside of the machine.
Another arrangement that is known to the present applicant comprises a mechanical rocker without elastic rigidity, but with frictional damping by means of corresponding guides. A fixed rod assembly which joins the two feet to one another is used for this purpose. The disadvantage here is that the system is dependent upon the installation space and foot spacing because of the fixed rod assembly.
U.S. Pat. No. 3,954,241 discloses a leveling system for an appliance, such as a washing machine, comprising appliance feet 14, 16 which are arranged at the underside of the appliance. Two of the appliance feet are accessible at the front end of the appliance and are adjustable in height by rotation within a thread and, in this way, allow the front end of the appliance to be adjusted in height and/or make it possible to adapt to uneven floors, while two rear appliance feet 16 enable automatic height compensation by means of a pull cable. The appliance feet 16 which are adjustable in height by means of the pull cable have, in each instance, a cylindrical housing that is fastened to the rear side near the underside or directly to the underside of the appliance. A piston carrying the appliance foot plate 34 is arranged in this cylindrical housing and the pull cable 18 connects the pistons of the two appliance feet 16 with one another. Under operating load, friction prevents a movement of the cable. The rear feet cannot be jointly changed in height in the same direction for adjusting the height of the appliance. This is disadvantageous for bottom stacking.
U.S. Pat. No. 4,770,275 discloses a leveling system for a ladder comprising feet 3 which are arranged at the underside 10 of the ladder and which are adjustable in height by means of an actuating member 4 in the form of a wire cable so that it is possible to adjust the height of the feet of the ladder mutually and accordingly adapt to uneven ground or floors. The actuating member is a traction member 4 and the feet 3, which are adjustable in height by means of the traction member 4, have, in each instance, a cylindrical housing 1 which is fastened to the underside of the ladder, a piston 3 carrying the foot plate 12 being arranged in the cylindrical housing 1. The piston 3 has a threaded bore hole for receiving a bolt 10 having at its ball-shaped end a foot plate 12 that is swivelable around the ball to a limited extent. In this case also it is not possible to change height in the same direction, which would also not be useful for a ladder. Again, the movement of the traction member is prevented under load by a friction arrangement. In addition, the feet of a ladder are always easily accessible so that the problem of inaccessible feet does not arise in this case.
This is a different matter when the domestic device is a household appliance in which at least two of the feet, namely, the rear feet, are inaccessible at least when the appliance is installed in a kitchen. In this case, it would also be useful if it were possible to carry out adjustment or, if necessary, pre-adjustment, of the height of the feet in the same direction in addition to leveling (in opposite directions) in order to compensate for uneven floors.
The system according to the above-cited DE 35 19 479 already has many basic advantages; for example, a self-regulating effect occurs in the arrangement between the two appliance feet in the rear area of the appliance. However, the known arrangement does not have sufficient long-term stability with respect to construction. Exactly dimensioned, closely toleranced metal component parts are required in order to maintain liquid pressure over long periods of time and are expensive to produce. When the system is leaky, it is impossible to restore the foot adjustment.